Undercover Lovahs
by shimmeryshine
Summary: Three times Castle and Beckett go undercover and it ends in sex  and one time it doesn't .


1.

This wasn't supposed to keep happening.

Castle would probably say that it took too long to _start_ happening, but she's not Castle, she's a _cop,_ and letting your partner put his hand inside your pants in the middle of an undercover operation is strictly Against Protocol.

That doesn't mean she doesn't groan and arch forward when he does it, though. Castle mouths her thumping jugular as she cants her head to the right, peering out the driver's side window of his roomy SUV. She hadn't even known he owned anything other than his flashy Ferrari, until he had come by to pick her up for their scheduled stakeout. An unmarked Crown Vic would stand out as much as a blue and white with sirens in this neighborhood, and Castle had been all kinds of gleeful to be in the driver's seat.

Which is where he still was, in between her legs with his fingers working a maddening rhythm exactly where she needs it.

"He's gone," she whispers, voice coming out hoarse and throaty. Her head is still tilted to the side, hand playing with the hair at the nape of his neck, unconsciously mimicking the movement of his fingers below. She closes her eyes for a minute, enjoying the feel of his tongue on her skin, teeth nipping lightly, fingers sliding just right. And then she _yanks_.

"_Ow_," he gasps, reflexively curling his fingers inside of her, making her bite her own lip.

"When I said _kiss me_, I didn't mean…" she trails off, gesturing at her lap with the hand not currently twisting in the back of his head.

"I was just trying to be authentic. Didn't want to blow our cover."

His smirk is maddening.

She rolls her eyes.

Before she can convince herself to swing back over into her own seat, Castle leans his face forward, staring her down, mouth a millimeter from her lips. He is utterly incapable of staying out of her personal space. "What _did_ you mean then, detective?"

His voice is so damn low she can feel it all the way down to her toes. Her eyes drop from his gaze to his mouth three times before she finally groans in assent, pulling his lower lip between her teeth and sucking.

"So you don't want me to stop then?" he whispers as she pulls her head away again, flicking her eyes toward the window.

"_Castle_." At the sound of his name he presses the heel of his palm sharply against her, rubbing away the edge in her voice. "I'm supposed to be watching the house."

He can tell that she's legitimately conflicted about dropping the ball on her job, her very serious, very important job, but she's been so wound up that he's pretty positive she needs this release just as badly as she needs to make sure this murder suspect doesn't sneak off into the night. "Keep your eyes open then," he says, the unexpected voice of reason.

Her mouth wants to smile at him, but instead she shifts forward enough so that he can't really see her expression, spreading her knees wider over his lap. "Faster," she breathes into his ear, egging him on with a tiny thrust of her hips.

She holds onto the back of his head as her eyes stare off into the distance, the streetlights blurring as his fingers pick up speed and she swallows down a sob of release.

* * *

><p>2.<p>

It's really, _really_ not her fault when it happens again in a dark corner of a club after Castle _shoots a drug dealer _in front of her. They'd been part of a sting, dressed to party as the rest of their team waited outside in a surveillance van, Castle griping in her ear about not being able to carry a gun as she tries and fails to dance in front of him without making any body contact.

"You're not a cop, Castle."

"But we're _undercover_, what if someone tries to shoot me? Or tries to shoot you and I can't have your back because you won't let me use a gun and then I jump in front of the bullet in an extremely heroic and gallant manner and end up _dead_."

She rolls her eyes at his overactive writers brain, tries not to stick on the fact that his entire argument involves jumping in front of a bullet for her.

"What are the odds of that happening?"

He winces. "Well now they're significantly higher because you just said that _out loud_."

"Castle."

Instead of continuing on his line of dramatics about carrying a gun, he suddenly shifts closer to her, voice dropping an octave. "Where is your gun anyway? I know you have it on you, but that dress is very small, and _very_ tight." His eyes drop from hers to sweep down her body for a moment before coming back up, looking curious and a little hazy around the edges.

Aroused?

His fingers are resting lightly against the slight swell of her hip now, and instead of answering, she curls her fingers around his wrist and slides his hand downward until it's resting along her upper thigh. His fingers rub at the material, feeling for the strap of her thigh holster, throat bobbing as he finds it. They make eye contact for a brief moment as he fingers the slight bump, and then his thumb is trailing her hem and brushing against the bare skin of her thigh. She sucks in a breath through her nose as he feels along the strap, her skin a casualty of his exploration, and then he's leaning in, nose brushing her cheek as he goes for her ear, entirely too close for an operation where they're being watched.

"Don't move," he says in this voice that doesn't match his words, and she's so distracted by his hands that she starts to ask _what_ when he's suddenly sliding his palm completely up her skirt and her eyes go wide as she realizes he's pulling free her _gun_ not trying to cop a feel and then he's yanking her into him and shooting at something over her head and her ears are ringing and her blood is pumping as she dazedly looks up at him. His neck is pulsing with the fast beat of his heart and he's still holding her gun in a death grip and it's all she can do to tear her eyes away from the sight of it to see _who he just shot_.

She's practically panting against him as she turns her body to see Ryan and Esposito rush through the door with a team behind them, guns drawn and pointed at the hunched body of the drug dealer they'd been surveilling. Esposito turns him over with a nudge of his shoe and the man groans, clutching his shoulder, his own gun snatched up by a uniform.

Beckett lets out a breath, glad that the man isn't _dead_ at Castle's hand and grabs her gun out of his grip and slides it quickly back into its holster. It's still warm, warm from being fired and warm from his hand and it practically burns against the sensitive skin of her inner thigh as she straps it into place.

Esposito is shooting Castle a questioning glance as they drag the dealer out the door. "He had a gun pointed right at us!" he says, clearly exasperated that he's being questioned at all. There's going to be hell to pay with Gates when they get back to the precinct, but for now all Beckett can think about is the warm feel of the gun strapped between her legs and the way Castle's arm is still holding her firmly in place at his side.

"We'll give you our statements back at the precinct," Beckett throws at Esposito and then she turns, dragging Castle toward the back of the club where it's dark. There are long navy blue walls of fabric separating the entire back corner of the club into tiny secluded areas meant for _privacy_, and Beckett's heart races as she feels Castle bumping into her back from behind, following her entirely too closely.

"Where are we going?" he shouts into her ear over the thumping music, the breath from his mouth warming the shell of her ear in a way that makes her shiver. All she can do is picture him with that gun, with _her _gun, and it's what she's thinking about as she finally finds a suitable place and shoves him back behind a curtain and up against a wall.

"That was _stupid_," she growls at him, arching her entire front against his. He recoils a little bit, pressing his head against the wall, but then she's in his face, millimeters from his lips and he can't help but be drawn closer to her.

Before she can yell at him anymore, he reaches up to grab her around her biceps, spinning them so their positions are reversed with her pressed against the wall and him looming above her.

"He was going to _shoot you_."

"You could have _told me that_ instead of _shooting him_."

She can see that she's pissing him off, the clench of his jaw clear as day when he's this close to her, but she can't stop. He wasn't even _wrong_. If he had pushed her to the side, whoever had been standing behind them would have been shot, and if he had taken the time to tell her about the man coming up behind her, it likely would have been too late but her blood is screaming with lust and she doesn't _want_ it to be and so she grabs his shirt roughly in her fists and pulls him impossibly closer, eyes narrowing angrily.

"What's the matter Beckett," he spits out, resting an open palm right by the side of her head. "Can't handle being saved once in your _life_?"

She wants to hit him but instead she yanks him even closer and crushes her mouth to his, grunting around it as he raises a hand to the back of her neck, possessively holding her to him. Her mouth opens immediately as his tongue strokes in, fighting with her for control of the kiss, control she's not giving up. She grips the back of his neck in the same way he's gripping hers, almost pinching she's holding on so tightly. She can feel his jaw working there, trying to take her kiss by kiss until he somehow slides those damn hands up her dress again and she's trying to jump up onto him but her gun is completely and totally in the way. His fingers play with it as he kisses down her jaw, impatient huffs of air spilling from her lips.

"So how exactly turned on are you from watching me shoot that drug dealer?" he asks cockily against the skin behind her ear, using his tongue to brand the words into her flesh.

She is _livid_ that he's figured her out so effortlessly. Her fingers fist in the back of his hair, tugging him back to look at her, but she doesn't answer him.

"Just – move my gun out of the way."

He grins maddeningly at her non answer, and she knows it's only a matter of a couple of seconds before he can deduce exactly how turned on she is, but until then she bites her lip at the drag of canvass on her thigh as he slowly turns the holster to the side so her gun is lying against the back of her leg and out of the way.

"You put the safety back on, right?" he asks her in his best bedroom voice and _fuck _if it doesn't completely do it for her.

"Yes."

He leans back in to deliberately capture her lips and somehow this has turned into him indulging her thing for guns willingly instead of her taking what she wants from him while he fumbles to keep up. It's so good and so, _so_ bad all at the same time.

His hands are back on her thighs then, both of them, as he hoists her up and then she hears the teeth of his zipper separate, or at least she thinks she does as the music thumps around them and he pushes her underwear to the side and drags a long finger against her and the kiss he gives her is _hard_ at the evidence he finds between her legs and then she feels him there, hard and thick with want for her. She practically sobs as he pins her against the wall, not being gentle because she really, really does not want him to be, and it's an embarrassingly short amount of time before she's burying her face into his neck and trying not to scream. He follows right behind her though, the fingers on her thigh so close to her gun she almost wants to tell him not to stop, that she's not done, but then he's letting her slide down the wall and back to her feet and they both stand there panting for a moment as he straightens himself.

When he reaches back under her dress for her holster, she lets him, savoring the scratch of fabric against the too sensitive skin on the inside of her thigh until her gun is in place again.

Once she's situated, he leans back into her one last time, pinning her to the wall with his stare.

"Just so you know, I'm never going to be able to look at your gun again without thinking about what it does to you."

Her eyes slide closed at his confession, thigh flexing against her holster under her dress.

_Me too, Castle_ she wants to say. _Me too._

* * *

><p>3.<p>

Someone at the precinct thinks they're _hilarious_ when they assign Castle and Beckett to a house in the suburbs for the weekend, alone, to investigate a string of suspicious deaths in the neighborhood.

Ryan and Esposito can barely keep it together when she emerges from the bathroom, tugging awkwardly at the collar of her bright blue polo shirt and pink cardigan, but Castle only has eyes for the hem of her Khaki skirt, falling to a respectable length mid thigh, but he sees her in skirts so rarely that the sight of any bare leg is enough to drive him to distraction.

She notices and rolls her eyes. "Suburban mom look really doing it for you there Castle?" she asks him, voice deadpan and unamused.

His eyes jerk up from her legs, looking a little bit sheepish, and then it's his turn to awkwardly adjust his new clothes – a grey sweater vest over a colorfully checked button down and khaki pants. They look sickeningly matched.

Ryan interrupts their uncomfortable moment as he approaches with a small wooden box, and when he opens it up to them, Beckett wants to hurl.

"Time to get hitched," he says, lips pressed into a tight line to keep from laughing at them. Beckett reaches in and grabs her ring before Castle can get any ideas about putting it on her finger for her and then stalks off toward the elevator without waiting for him.

She doesn't have to be looking at him to know what his face looks like.

.

"Oh my god this is so boring, what do people even _do_ in the suburbs?" Beckett whines as she flops down on their fake bed in their fake bedroom in their fake house and flings an arm over her eyes. She's still wearing her suburban mom getup, fresh from the backyard barbecue they'd been forced into attending to scope out their new neighbors.

Castle shrugs at her even though she's not looking at him. "Have a lot of sex? That's why there are so many kids everywhere."

She snorts behind her hand. "Sounds like you're speaking from personal experience."

"I have spent some time in the suburban trenches, I'm not going to lie."

She rolls her eyes because it sounds like a _brag_. The mattress depresses beside her as he sits down, and she finally removes her arm from over her eyes. He's watching her, a twinkle in his eye from their conversation, but he doesn't move closer so she sits up, closing some of the distance between them.

"Well you can show me how it's done then." Her bedroom voice goes straight through him, she can tell, and then she's reaching up to finger the stiff collar of his shirt.

He reaches up to grab her wrist, stilling her motion. "I thought we were going to stop doing this?" he breathes out roughly, voice only sounding mildly questioning, like he doesn't even believe it himself.

She scoots closer.

"Come on Castle, what _else_ are we going to do?" He looks unsure for about a second, and then she feels the hot slide of his palm on her bare thigh, dragging her leg up and over his until she finds herself straddling him on the bed. She grins and leans in to whisper in his ear. "Show me."

She both hears and feels his groan as he abruptly pulls her farther into his lap with one hand and uses the other to pull her head to his and crush a kiss to her lips, all hesitation erased. She hums into the kiss as she shoves her hands under his sweater vest, yanking it up until he has to separate from her to get it off. It flings across the room and lands somewhere on the floor, and then his hands are shoving off her bubblegum pink cardigan and sliding along her bare back under her polo shirt. She huffs annoyedly as the collar repeatedly bumps against her chin as he rucks it up, still kissing her with long, sure strokes of his tongue.

"Take this _off_," she breathes into his mouth, frustrated that she's still wearing the clothes she's wanted to rip off since the second she put them on in the precinct bathroom.

He obeys, pulling the offending garment up and over her head as he lets his gaze drop to the black bra she's wearing, and her abdominals jump as she feels the heat of his stare work over her. They've never done this with the lights on.

"Can we leave the skirt on?" he asks into her collarbone as his tongue licks out hotly against her skin. His fingers are playing just under the hem of said skirt, drawing light shapes along her thighs.

Her hips shift against him at the feeling and his request, betraying her arousal. "_No_," she says sharply. "Take it off, take it _all_ off."

She can feel him smiling irritatingly against the skin of her chest now. "Someone's eager…"

She shoves him backward for his tone, standing and dropping her own skirt without his help. She uses a finger to gesture to his entirely too clothed body. "Off," she orders and then they're both stripping and falling back into the bed blissfully _naked_.

It's fast then, he's pinning her to the mattress with a hand linked together with hers over her head and all she can feel as he presses into her is the bite of the ring on his finger. They're both still wearing them, everything else gone onto a pile on the floor but they've both forgotten the rings and she gasps as she feels his rub against the space in between her fingers, as solid and present as he is between her legs, and when she comes she's clutching at his hands, feeling her own ring scrape across her skin, across his and she doesn't know what it means that the presence of them just completely up and swept her away.

.

She lets him spoon her afterward, thumb still distracted with the band on her finger, and only gets up after he's fallen asleep. Their clothes litter the floor but the ring shines brightly on his finger and she has to remove herself from the room for fear of the things churning inside of her guts. She grabs his loud button down shirt before she can think twice about it and buttons three of the buttons, curling against it as she breathes in the smell of him. As she slowly makes her way down the staircase toward the kitchen for some water, the ring weighs heavily on her finger.

* * *

><p>4.<p>

He's _so_ jealous when Gates insists that Beckett go undercover with one of the agents from the DEA when their case takes a turn toward the organized drug trade one Thursday afternoon. He even argues with Gates about it, throws around words like _partner_ and _excellent under pressure_ and Beckett has to put a hand on his arm to reel him back when Gates looks like she's ready to eject him from the precinct for good.

"Can I talk to you?" she says sharply, shooting him a look that says _calm down_, and then he's following her into the break room as she shuts the door behind her. He's vibrating with tension, and she tries to bring him down with just a look, a steady lock of eyes that draw them to each other like magnets. It mostly works.

"Beckett I should be in there with you," he half whispers, gesturing back in Gate's direction.

"This is a serious drug cartel, Castle. The only reason they're letting _me_ go in is because they wouldn't have even connected the drugs to these guys if not for that ledger we found."

"_We_ found."

Her eyes soften a little bit, she's not unfamiliar with the feeling of being unceremoniously excluded from a case.

"Castle. I promise you it'll be fine, you can watch from the van with Ryan and Esposito."

He crosses his arms, looking none to happy about being demoted to the _van_. She watches him glance back out the window at the DEA agent circling her desk. "Who even _is _that guy anyway, do we know anything about him? I don't like you going in there with him when we don't even know who he is."

She tilts her head curiously at him, sees the tendons in his neck tighten as his eyes follow the other man's every move.

She's about to go undercover with another man. Without him. _Oh_.

"Castle…" at the sound of his name, he turns his eyes back to her, looking dejected. She's not quite sure when this thing they've been doing became _this_, but she finds herself unable to stop the reach of her hand, the way it rests against his forearm. "Castle, it's not like how it is with us."

She shifts kind of uncomfortably at the admission, but the sharp cut of his eyes and the way he focuses on her is almost worth it. They don't talk about this.

"Have dinner with me after the sting," she blurts out, desperate to prove to him that he's not some kind of afterthought. That she would _never_ betray him for someone else.

"Dinner?"

"Just me and you, no undercover, no cops."

"Just us."

"Just us."

Her palms are suddenly sweaty because she's pretty sure she just asked Richard Castle out on a _date_ and this is so absurd because they've sort of been sleeping together for like a year but she wants him away from their jobs more than she's ever let herself contemplate.

She does always need a _push_ to break her habits.

"Okay," he says, a tiny smile hiding out in the corners of his lips.

"Have my back from the van?" she asks, gesturing back toward the bullpen.

"I'm not taking my eyes off that guy."

She rolls her eyes.

"What? I'm not."

"Come on, Castle." She leads him back out to her desk and tries not to laugh as he puffs out his chest and eyes the DEA agent, posturing so obviously that _everyone_ is going to realize what he's doing if they don't get a move on.

As she starts to walk toward the elevator she hears Esposito slide up beside him, watches as he gives the DEA agent a squinty once over. "Don't worry bro, we've got your back," he says to Castle out of the side of his mouth and then Ryan is there nodding conspiratorially and she hides a smile behind her knuckles because apparently the only thing _undercover_ about what she and Castle have been doing is that it happened when they were supposed to be pretending to be other people.

(He may be a famous fiction writer, but she's always been one for reality.)


End file.
